Loaders have the facility for coupling and uncoupling an attachment with a lifting arm or for switching between various attachments such as a bucket, a clamp, or a fork.
A coupler is used to couple the attachment with the lifting arm. Hydraulically powered displaceable pins are generally used for the attachment coupler's locking. Namely, the attachment is guided so that the locking holes are situated in a position in which displaceable pins can be shot through them, following which these pins, guided by controls located in the operating station, are hydraulically activated and shot into the holes, thereby locking the attachment with the lifting arm.
The hydraulically powered locking enables relatively rapid change of attachments without leaving the operating site, but it requires various hydraulic components such as actuators, conduits and valves, thus making a complex structure. Also, the engine and the whole machine should be turned on since this hydraulic coupler depends upon existing machine hydraulics for activating the locking pins.
On the other hand, manual couplers are relatively simple in structure, but they require substantial efforts and time from users for coupling or uncoupling for each and every locking position between the bracket and the attachment.